Distribution and Dynamics of Radionuclides in the Chernobyl Cooling Pond

Abstract

As a result of the accident at the Chernobyl Nuclear Power Plant (ChNPP) in 1986, the Cooling Pond (CP) was heavily contaminated by radionuclides due to atmospheric fallout and discharges from the industrial site. Shortly afterward, most of the radionuclides were deposited to the CP bottom sediments and later served as a source for secondary contamination of the water column. By the end of the initial phase, 137Cs and 90Sr activity concentrations in the CP water began to decrease until decommissioning of the pond. This decrease of radionuclide activity concentrations in water was due to radioactive decay, sedimentation of radionuclides onto the bottom, dilution of pond’s volume with water pumped from Pripyat River, and 90Sr infiltration through the dam. Draining of CP began in May 2014, resulting in splitting the pond into three separate parts and the water surface area reduction by some 40% by the end of 2017. Later on, 90Sr activity concentration in the water of the Northern and Western sectors increased by a factor of 3 at the end of 2017, while in the Southern sector the 90Sr water activity concentration increased by less than 10–15%. In future, 90Sr activity concentration in the CP water is expected to further go up due to dissolution of fuel particles at drained territories causing wash-off of the radionuclide by surface runoff to residual lakes.